Can we use serial communication in arduino only for RX pin
HardwareSerial takes over the Tx and Rx pins. However you can use SoftwareSerial. 

Arduino forum user whiteglint143 made an adaptation of SoftwareSerial that does read-only.

http://gammon.com.au/Arduino/ReceiveOnlySoftwareSerial.zip

See Receive Only Software Serial  - Arduino Forum




  You can regain control over the TX or RX pins by unsetting the TXENn or RXENn bit in the UCSRnB register.


Like this?

const byte LED = 1;

void setup ()
  {
  Serial.begin (115200);
  Serial.println ();
  UCSR0B &amp;= ~bit (TXEN0);  // disable transmit
  Serial.println ("Testing");
  pinMode (LED, OUTPUT);
  }  // end of setup

void loop ()
  {
  digitalWrite (LED, HIGH);
  delay (500);
  digitalWrite (LED, LOW);
  delay (500);
  }  // end of loop


Gerben's suggestion works, in a sense. The pin flashes, but rather disconcertingly, the Tx LED on the board also flashes, out of sync with pin 1. Clearly the signal is making its way to the ATmega16U2 chip, which then flashes the indicator LED. This may not be desirable if you have something connected to the serial port, as it may be interpreted as low-speed serial communications.